1. Technical Field
The present disclosure relates to a permanent magnet synchronous motor, and more particularly relates to an apparatus for measuring a position of a rotor of a permanent magnet synchronous motor.
2. Description of Related Art
Generally, a brushless electric motor can be divided into a permanent magnet synchronous motor and a DC brushless motor according to different counter electromotive forces. Particularly, the permanent magnet synchronous motor has a sine-wave counter electromotive force, and can generate a constant torque through a sine-wave stator current.
However, when the permanent magnet synchronous motor (PMSM) is operated, coupling thereof exists between a d-axis magnetic circuit and a q-axis magnetic circuit under a rotary coordinate system (d-q axes), so that an actual inductance matrix of the PMSM is not as same as the inductance matrix obtained by a decoupling analysis on the d and q axes, which results in a certain angle deviation in a method for measuring or estimating an angle of the rotor position through a model of salient-pole motor, and further influences the control effect, especially influencing the control performance under an overload condition.
In order to solve the aforementioned problem, the prior art mostly uses a method of analyzing electromagnetic fields. That is, the acquired parameters of a motor main body is analyzed and calculated to obtain a cross-saturated inductance value or angle error values under different d-q axes currents, so as to perform angle compensation.
However, the aforementioned method requires a large amount of calculation and depends on the accuracy of the parameters of the motor main body, and the parameters of the motor main body always cannot be obtained precisely, so that the aforementioned method is not generally applicable.
Moreover, for a method for actually measuring the angle deviation caused by a saturation effect, it usually needs to inject voltages or currents of different amplitudes and thus certain torques are generated. Meanwhile, in order to keep the motor in a standby state, an additional equipment (e.g., a mechanical internal contracting brake apparatus) is required to lock the motor. As a result, problems such as inconvenience for utilization and poor efficiency are caused in actual operation, also resulting in the condition of limiting the measuring method and limiting the utilization thereof in certain situations, thereby reducing the flexibility of usage and directly increasing the difficulty in application of the aforementioned measuring method.